The general goal of this project is to use biochemical and genetic engineering techniques to optimize the immunogenicity of HIV peptide immunogens in order to ask critical questions relevant to HIV vaccine development and to determine HIV peptide immunogen feasibility as vaccine candidates for induction of mucosal and systemic anti-HIV immunity. Using HIV envelope Th-B-CTL epitope T1-SP10(A) gp120 V3 loop peptides as prototype experimental immunogens, we will study a series of bacterial carrier proteins and Salmonella sp. live vectors for their ability to enhance HIV subunit immunogenicity. The specific aims of Project 4 are: 1) we will covalently couple T1SP10 (A) peptides onto carrier proteins such as CRM197, a non-toxic variant of diphtheria toxin, non-toxic CRM of pertussis toxin, filamentous hemoagglutinin (FHA) from B. Pertussis, flagella from Salmonella typhi, and VP6 from rotavirus; 2) We will express HIV Th-B-CTL epitopes in the hypervariable region of the H1-d flagellar gene of Salmonella muenchen expressed in attenuated Salmonella typhimurium or Salmonella typhi for use as systemic and mucosal immunogens; 3) We will express HIV Th-B-CTL epitopes in attenuated Salmonella typhimurium or Salmonella typhi as fusion proteins with the B subunit of the heat labile toxin of E. coli, or with the low molecular weight outer membrane protein of H. influenzae, and in surface exposed loops of Salmonella typhimurium outer membrane porin (OmpC); and 4) Prototype HIV env T1-SP10(A) peptides in various forms from aims 1 and 2 above will be incorporated into liposomes containing either an adjuvant, monophosphoryl lipid A and/or the bacterial integrin-binding protein, invasin, to target the delivery of the liposome to mucosal surfaces of the gastrointestinal tract. The new immunogens developed in Project 4 will be studied in mice, and their ability to induce Th1, Th2 types of helper T cell responses, Class I-restricted CTL and B cell anti- HIV neutralizing antibodies determined.